藻类对BPA的降解.docx

1、藻类对BPA的降解Statement of novelty Freshwater microalgae Chlamydomonas mexicana and Chlorella vulgaris promoted the bioaccumulation/biodegradation of an endocrine disrupting chemical bisphenol A. C. mexicana was more tolerant to BPA and grew at concentrations of BPA up to 50 mg L-1, which is beyond its c

2、oncentration range detected in the natural contaminated aquatic systems. FAME and carbohydrate content in both microalgae increased on exposure to BPA, generating a potential biofuel feedstock. This study showed the potential of C. mexicana to treat the BPA contaminated sites with simultaneous biofu

3、el feedstock production.Highlights A dual strategy for BPA remediation and biofuel feedstock production C. mexicana was more tolerant to BPA than C. vulgaris Microalgae promoted bioaccumulation and biodegradation of BPA BPA increased the FAME and carbohydrate content of microalgaeBiodegradation of b

4、isphenol A by the freshwater microalgae Chlamydomonas mexicana and Chlorella vulgarisMin-Kyu Jia, Akhil N. Kabraa, Jaewon Choib, Jae-Hoon Hwanga, Jung Rae Kimc, Reda A. I. Abou-Shanabd, Byong-Hun JeonaaDepartment of Environmental Engineering, Yonsei University, Wonju 220-710, South KoreabWater Analy

5、sis and Research Center, Korea Institute of Water and Environment, Korea Water Resources Corp.,Daejeon 306-711, South KoreacSchool of Chemical and Biomolecular Engineering, Pusan National University, Busan, 609-735, South KoreadDepartment of Environmental Biotechnology, City of Scientific Research a

6、nd Technology Applications, New Borg El Arab City, Alexandria 21934, Egypt*Corresponding author. Tel: +82 33 760 2446; Fax: +82 33 760 2571 E-mail address: bhjeonyonsei.ac.kr (BHJ)Abstract The endocrine-disrupting chemical, bisphenol A (BPA) has attracted much attention due to its estrogenic activit

7、y and widespread environmental distribution. The toxicity and cellular stresses of BPA to Chlamydomonas mexicana and Chlorella vulgaris and its biodegradation/bioaccumulation by both microalgae were investigated. The 120-h EC50 of BPA for C. mexicana and C. vulgaris were 44.8 and 39.8 mg L-1, respec

8、tively. The dry cell weight and chlorophyll a content of both microalgae decreased with increasing BPA concentration higher than 10 mg L-1. Growth of C. vulgaris was signicantly inhibited at 50 mg L-1 BPA compared to C. mexicana. Total nitrogen (TN) and total phosphorous (TP) removal was higher in C

9、. mexicana than in C. vulgaris. Microalgae performed the bioaccumulation and biodegradation of BPA to varying extents at different initial BPA concentrations. The highest rates of BPA biodegradation, 24 and 23% by C. mexicana and C. vulgaris, respectively, were achieved at 1 mg L-1 BPA. Both the tot

10、al fatty acid and carbohydrate contents increased with increasing BPA concentration. This study demonstrated that C. mexicana was more tolerant to BPA and could be used for treatment of BPA contaminated aqueous systems.Keywords: Bisphenol A, Biodegradation, Microalgae, Carbohydrates, Fatty acids1. I

11、ntroductionPopulation growth and urbanization together with parallel global industrialization have resulted in significant contamination of water streams with a wide variety of endocrine-disrupting chemicals (EDCs) 1. Bisphenol A(BPA), which is employed for the production of epoxy resins and polycar

12、bonate (PC) plastics, is utilized in various food and drink packaging, baby bottles and dental sealants 2. BPA is a strong endocrine disruptor and also leads to carcinogenesis 3. Despite its hazardous effects, BPA has been extensively used, increasing its global consumption at an annual rate of 5.5%

13、 during 2009-2012 4. It has been reported that humans are primarily exposed to BPA by ingestion, inhalation and skin contact on the order of micrograms per kilogram of body weight daily 5. BPA released from manufacturing sites or its residues from urban and industrial wastewater severely contaminate

14、 the environment, primarily its aquatic systems. BPA has been detected at concentrations of approximately 150 g L1 in industrial wastewaters 6, 21 g L1 in rivers 7 and 17,200 g L1 in landll leachates 8. BPA imposes deleterious effects on aquatic organisms, even at concentrations of less than 1 g L1

15、9, making its detection and removal to non-toxic level a primary concern in water quality management. Methods to remove environmental pollutants, especially BPA include photo-degradation 10, oxidation 11, photoelectrocatalytic oxidation 12 and biodegradation 13. Phytoremediation is a solar power-dri

16、ven, ecologically sound and sustainable reclamation strategy that uses plants for cleaning contaminated sites 14. In recent years, phytoremediation of contaminated waters by photoautotrophic aquatic organisms such as algae, has been demonstrated to be successful for the removal of both organic and i

17、norganic pollutants 15,16. As primary producers and residing at the base of aquatic food chains, microalgae play an important role in maintaining the balance of aquatic ecosystems; however, they are known to be relatively sensitive to chemicals 17. Microalgae have been reported to accumulate polluta

18、nts such as heavy metals, hexachlorobenzene, herbicides, insecticides and phenol 15,18. The biodegradation of environmental organic contaminants by algae has also been reported 19,20, indicating that algae have the potential to remove pollutants from wastewater and can be employed in wastewater trea

19、tment facilities. Microalgae and marine diatoms have been reported for the remediation of BPA 13,21, but relatively few studies have reported the utilization of freshwater microalgae to remove BPA. This study aims to investigate (1) the screening of BPA tolerant algal strains; (2) microalgal bioaccu

20、mulation/biodegradation of BPA; and (3) the effect of BPA concentration on nutrient (nitrogen and phosphorous) removal and carbohydrate and fatty acid production by microalgae.2. Materials and Methods2-1. ChemicalsAll chemicals used in this study were of analytical grade. BPA (purity, 99.0%) was pur

21、chased from Sigma-Aldrich (St. Louis, MO, USA), and methanol and other chemicals were obtained from Duksan (Seoul, S. Korea).2-2. Algal strains, culture conditions and inoculum preparationFour microalgal species were investigated in this study: Chlamydomonas mexicana FR751193, Chlorella vulgaris FR7

22、51187, Micractinium reisseri FR751194 and Scenedesmus obliquus HM103383 (Table 1). The microalgal strains were individually inoculated in 250 mL Erlenmeyer flasks containing 100 mL Bolds Basal Medium (BBM) at 10% concentration (Vinoculum/Vmedia). The microalgal cells were cultivated in a shaker incu

23、bator at 150 rpm and 27 C under continuous illumination of white fluorescent light of 45-50 mol photon m-2 s-1 for two weeks. The microalgal suspension was adjusted to an absorbance of 1.0 at an optical density (OD) of 680 nm as measured using a spectrophotometer (Hach DR/4000, Loveland, CO, USA). 2

24、.3. Experimental procedureFor growth inhibition tests, the toxicity of methanol to the algal cells was investigated. The initial concentration of methanol in the medium was 0.03% (v/v). Algal cells at the exponential phase were inoculated into the medium supplemented with different BPA concentration

25、s. The effective concentration of BPA that produced a 50% inhibition of algal growth at 120 h (120-h EC50) was obtained from the dose-response regression curve by plotting BPA concentrations against inhibition percentages 22. Initial experiments were carried out to select BPA tolerant microalgal spe

26、cies with the lowest growth inhibition based on their biomass yield after 5 days of cultivation at 7 mg L-1 BPA in BBM. Furthermore, BPA removal and changes in the biochemical composition of selected microalgal species at 1, 5, 10, 25 and 50 mg L-1 BPA were determined. The batch experiments were con

27、ducted using 500 mL aluminum crimp-sealed serum bottles containing 300 mL BBM inoculated with 1.5% of the inoculum (Vinoculum/VBBM). The bottles were incubated in a shaker incubator at 27 C and 150 rpm, under white fluorescent light illumination (alternate light/dark periods of 16 h/8 h) at an inten

28、sity of 45-50 mol photon m2 s1 for 10 days. 2-4. Measurement of cell growth and nutrient removalGrowth was monitored based on changes in the OD680 concentration. The OD680 values were converted to dry cell weight (DCW) concentrations (g L-1), based on a linear relationship between OD680 and dry cell

29、 weight 23, which was obtained after extensive data analysis and was calculated by Eqs. (1) and (2) for C. mexicana and C. vulgaris, respectively, as follows:Dry weight (g L-1) = 0.3218 OD680 - 0.0139 (R = 0.9948) (1)Dry weight (g L-1) = 0.3065 OD680 - 0.0097 (R = 0.9958) (2)For the chlorophyll a me

30、asurement, a 5 mL culture was harvested by centrifugation at 4,500 g for 10 min. The supernatant was discarded and the pellet was re-suspended in 5 mL of 95% methanol, incubated at 60 C for 5 min and centrifuged again for 10 min. The absorbance of the supernatant at 665 and 652 nm wavelengths was de

31、termined with a Hach DR/4000 UV-visible spectrophotometer (Hach, Loveland, CO, USA), and the chlorophyll a concentration of the extract was calculated following the formula described by Porra et al. 24: Chlorophyll a (mg L-1) = 16.29 A665 8.54 A652 (3)The specific growth rate () was calculated by fi

32、tting the dry cell weight for the first 7 days of cultivation to an exponential function, as shown in Eq. 4: (4)TN and TP from the sample were measured using Persulfate Digestion and Acid Persulfate Digestion, which are equivalent to Standard Methods 4500-N C and 4500 P. B. 5, for water and wastewater, respectively 23. 2.5. Determination of residual BPA2-5-1. BPA in the medium and absorbed by cellsIn order to determine the amount of BPA in the medium, 10 mL of sample was collected from the culture and ce